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Date: Tue, 20 Feb 2018 22:01:13 +0100
From: Dominik Brodowski <linux@...inikbrodowski.net>
To: linux-kernel@...r.kernel.org, mingo@...nel.org, x86@...nel.org,
brgerst@...il.com, luto@...nel.org, jpoimboe@...hat.com
Cc: torvalds@...ux-foundation.org, ak@...ux.intel.com,
tglx@...utronix.de, dan.j.williams@...el.com
Subject: [RFC PATCH v3 6/6] x86/entry/64: open-code switch_to_thread_stack
Open-code the two instances which used switch_to_thread_stack. This
allows us to remove the wrapper around DO_SWITCH_TO_THREAD_STACK.
While at it, update the UNWIND hint to reflect where the IRET frame is,
and update the commentary to reflect what we are actually doing here.
Signed-off-by: Dominik Brodowski <linux@...inikbrodowski.net>
---
arch/x86/entry/entry_64.S | 76 +++++++++++++++++++++-------------------
arch/x86/entry/entry_64_compat.S | 17 +++++++--
2 files changed, 55 insertions(+), 38 deletions(-)
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 42a4b652469d..d5c7f18f79ac 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -538,17 +538,48 @@ END(irq_entries_start)
.endm
/*
- * Switch to the thread stack. This is called with the IRET frame and
- * orig_ax on the stack. (That is, RDI..R12 are not on the stack and
- * space has not been allocated for them.)
+ * Interrupt entry helper function.
+ *
+ * Entry runs with interrupts off. Stack layout at entry:
+ * +----------------------------------------------------+
+ * | regs->ss |
+ * | regs->rsp |
+ * | regs->eflags |
+ * | regs->cs |
+ * | regs->ip |
+ * +----------------------------------------------------+
+ * | regs->orig_ax = ~(interrupt number) |
+ * +----------------------------------------------------+
+ * | return address |
+ * +----------------------------------------------------+
*/
-.macro DO_SWITCH_TO_THREAD_STACK
+ENTRY(interrupt_entry)
+ UNWIND_HINT_FUNC
+ ASM_CLAC
+ cld
+
+ testb $3, CS-ORIG_RAX+8(%rsp)
+ jz 1f
+ SWAPGS
+
+ /*
+ * Switch to the thread stack. The IRET frame and orig_ax are
+ * on the stack, as well as the return address. RDI..R12 are
+ * not (yet) on the stack and space has not (yet) been
+ * allocated for them.
+ */
pushq %rdi
+
/* Need to switch before accessing the thread stack. */
SWITCH_TO_KERNEL_CR3 scratch_reg=%rdi
movq %rsp, %rdi
movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp
- UNWIND_HINT sp_offset=16 sp_reg=ORC_REG_DI
+
+ /*
+ * We have RDI, return address, and orig_ax on the stack on
+ * top of the IRET frame. That means offset=24
+ */
+ UNWIND_HINT_IRET_REGS base=%rdi offset=24
pushq 7*8(%rdi) /* regs->ss */
pushq 6*8(%rdi) /* regs->rsp */
@@ -560,25 +591,6 @@ END(irq_entries_start)
UNWIND_HINT_FUNC
movq (%rdi), %rdi
-.endm
-
-/*
- * Interrupt entry/exit.
- *
- * Interrupt entry points save only callee clobbered registers in fast path.
- *
- * Entry runs with interrupts off.
- */
-/* 8(%rsp): ~(interrupt number) */
-ENTRY(interrupt_entry)
- UNWIND_HINT_FUNC
- ASM_CLAC
- cld
-
- testb $3, CS-ORIG_RAX+8(%rsp)
- jz 1f
- SWAPGS
- DO_SWITCH_TO_THREAD_STACK
1:
PUSH_AND_CLEAR_REGS save_ret=1
@@ -592,7 +604,7 @@ ENTRY(interrupt_entry)
*
* We need to tell lockdep that IRQs are off. We can't do this until
* we fix gsbase, and we should do it before enter_from_user_mode
- * (which can take locks). Since TRACE_IRQS_OFF idempotent,
+ * (which can take locks). Since TRACE_IRQS_OFF is idempotent,
* the simplest way to handle it is to just call it twice if
* we enter from user mode. There's no reason to optimize this since
* TRACE_IRQS_OFF is a no-op if lockdep is off.
@@ -609,6 +621,9 @@ ENTRY(interrupt_entry)
ret
END(interrupt_entry)
+
+/* Interrupt entry/exit. */
+
/*
* The interrupt stubs push (~vector+0x80) onto the stack and
* then jump to common_interrupt.
@@ -878,17 +893,6 @@ apicinterrupt IRQ_WORK_VECTOR irq_work_interrupt smp_irq_work_interrupt
*/
#define CPU_TSS_IST(x) PER_CPU_VAR(cpu_tss_rw) + (TSS_ist + ((x) - 1) * 8)
-#if defined(CONFIG_IA32_EMULATION)
-/* entry_64_compat.S::entry_INT80_compat expects this to be an ASM function */
-ENTRY(switch_to_thread_stack)
- UNWIND_HINT_FUNC
-
- DO_SWITCH_TO_THREAD_STACK
-
- ret
-END(switch_to_thread_stack)
-#endif
-
.macro idtentry sym do_sym has_error_code:req paranoid=0 shift_ist=-1
ENTRY(\sym)
UNWIND_HINT_IRET_REGS offset=\has_error_code*8
diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index 364ea4a207be..e811dd9c5e99 100644
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -347,10 +347,23 @@ ENTRY(entry_INT80_compat)
*/
movl %eax, %eax
+ /* switch to thread stack expects orig_ax and rdi to be pushed */
pushq %rax /* pt_regs->orig_ax */
+ pushq %rdi /* pt_regs->di */
+
+ /* Need to switch before accessing the thread stack. */
+ SWITCH_TO_KERNEL_CR3 scratch_reg=%rdi
+ movq %rsp, %rdi
+ movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp
+
+ pushq 6*8(%rdi) /* regs->ss */
+ pushq 5*8(%rdi) /* regs->rsp */
+ pushq 4*8(%rdi) /* regs->eflags */
+ pushq 3*8(%rdi) /* regs->cs */
+ pushq 2*8(%rdi) /* regs->ip */
+ pushq 1*8(%rdi) /* regs->orig_ax */
- /* switch to thread stack expects orig_ax to be pushed */
- call switch_to_thread_stack
+ movq (%rdi), %rdi /* restore %rdi */
pushq %rdi /* pt_regs->di */
pushq %rsi /* pt_regs->si */
--
2.16.2
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